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Abstract: Rodríguez-Ramírez and Yáñez-Camacho (2008), Rodríguez-Vidal et al. (2009) and Rodríguez-Ramírez et al. (2009) have kept an ongoing discussion about the validity of radiocarbon ages in reconstructing Holocene palaeogeographical models in the Gulf of Cadiz. The discussion considered the validity and correctness of the ΔR value to be used in the area to calibrate radiocarbon ages of marine samples. These papers suggest that the ΔR value proposed by Lario (1996) and Dabrio et al. (1999, 2000) is erroneous, and consequently, that all the evolutionary models based on radiocarbon ages from marine samples that have been proposed in this area since 1996 must be revised. However, the papers commented here use erroneously the R, regional R and ΔR values. After reviewing the published data, it is apparent that the most reliable values of ΔR in the Gulf of Cadiz for middle-late Holocene samples range between ΔR =35±85yr and ΔR =95±15yr. This means that the values used in Lario (1996) and Dabrio et al. (1999, 2000) fall in this range, and also that the calibrated ages used by several authors adopting these values are fully reliable. Calibrations using ΔR values inside this range do not yield significant differences in terms of geological age owing to the magnitude of errors resulting from the methods employed. [ABSTRACT FROM AUTHOR]

Abstract: The well-exposed systems of prograding beach ridges on the Carchuna–Calahonda (Granada) and Campo de Dalías–Roquetas (Almería) coastal plains continue offshore as infralittoral prograding wedges (IPW). The Holocene IPW is a narrow morpho-sedimentary unit up to 2.5 km wide which develops seaward from the lower edge of the shoreface to 15–20 m depth, extending to a well-defined break of slope at water depths of 35–40 m. These IPWs have been recognized and studied using very high-resolution seismic profiles (TOPAS) and multibeam data (EM-3000D). In detail they are complex morpho-sedimentary units in which internal structures are closely linked to the pattern of progradation of the adjacent coastal plains. When longshore currents produce significant littoral drift, the IPWs are composed of several minor units arranged in offlap, which accrete parallel or oblique to the main shoreline. Therefore, it is possible to correlate progradational units in the coastal plain (H-units, sensu[Goy, J.L., Zazo, C., Dabrio, C.J., 2003. A beach-ridge progradation complex reflecting periodical sea-level and climate variability during the Holocene (Gulf of Almería, Western Mediterranean). Geomorphology 50, 251–268]) and subunits in the IPW, but special care is required depending on the local arrangement of morpho-sedimentary units. Besides, it is not realistic to draw conclusions regarding the age of the subunits inside a given IPW without adequate dating, as the number of subunits will greatly vary from place to place depending on local factors, magnitude of sea-level oscillations, and sediment supply. [Copyright &y& Elsevier]

Facies and geochemical analysis applied to marsh deposits are useful proxies for the reconstruction of aridity for the last millennia. The comparison of facies and geochemical records among cores from the Almenara and Benicasim marshes allows to identify changes in water level (Si/Al, Al, Ca) and salinity of the feeding waters (Mg/Al, Na/Al, S/Al). These changes, in turn, represent fluctuations in the position of the saline-fresh groundwater boundary, which can be related to variations in sea level and rainfall. For the last 4000 years, three events recording higher salinity conditions (ca. 3.4 ka BP, ca. 3 ka BP and ca. 1.8 ka BP) are noticeable in the record. Comparison to other studies around the Western Mediterranean basin allows us to correlate these events to arid episodes and to identify their forcing mechanisms. These aridity events are correlative to small falls in solar activity and Surface Sea Temperature (SST) during positive North Atlantic Oscillation (NAO) periods. Despite the small magnitude of these changes, the sensitivity of the system amplified the result providing a conspicuous signal. [ABSTRACT FROM AUTHOR]

Abstract: Many on-shore studies focused on high energy marine events occurred in the Gulf of Cadiz have been published since the 1990s. Most of the findings came from sedimentary, palaeontological and geomorphological records on estuaries, marshes, beach-barriers (spit-bars), and some coastal lowlands. Recent off-shore investigations in SW Iberia considered turbidite deposits as a proxy to recognise palaeoearthquakes in this zone. The comparison of datasets from both on-shore and off-shore records indicate that at least five tsunami events generated by strong earthquakes affected this area during the last 7000 years, previous to the more recent and well-documented 1755 AD Lisbon earthquake tsunami event. The catalogue of Holocene palaeotsunami presented here is supported by geological and geomorphological evidences, but also for archaeoseismic and palaeoseismic evidence and written reports for the more recent events occurred during historical times. The recurrence interval for these catastrophic events can be bracketed between 1200 and 1500 years. [Copyright &y& Elsevier]

Abstract: This paper presents a computational model for mapping the regional 3D distribution in which seafloor gas hydrates would be stable, that is carried out in a Geographical Information System (GIS) environment. The construction of the model is comprised of three primary steps, namely: (1) the construction of surfaces for the various variables based on available 3D data (seafloor temperature, geothermal gradient and depth-pressure); (2) the calculation of the gas function equilibrium functions for the various hydrocarbon compositions reported from hydrate and sediment samples; and (3) the calculation of the thickness of the hydrate stability zone. The solution is based on a transcendental function, which is solved iteratively in a GIS environment. The model has been applied in the northernmost continental slope of the Gulf of Cadiz, an area where an abundant supply for hydrate formation, such as extensive hydrocarbon seeps, diapirs and fault structures, is combined with deep undercurrents and a complex seafloor morphology. In the Gulf of Cadiz, the model depicts the distribution of the base of the gas hydrate stability zone for both biogenic and thermogenic gas compositions, and explains the geometry and distribution of geological structures derived from gas venting in the Tasyo Field (Gulf of Cadiz) and the generation of BSR levels on the upper continental slope. [Copyright &y& Elsevier]

Abstract: This study represents the first paleoseismic approach in Spain in which archaeological remains are considered. The ancient Roman city of Baelo Claudia (1st–4th centuries AD), located at the axial zone of the Gibraltar Strait (Cadiz, south Spain), contains abundant disrupted architectural relics and ground collapses (i.e. landsliding, liquefacion) probably related to historic earthquake damage of intensity IX–X MSK. The archaeological stratigraphy of the city evidence two major episodes of abrupt city destruction bracketed in AD 40–60 and AD 350–395 separated by an intervening horizon of demolition for city rebuilding, otherwise characteristic for many earthquake-damaged archaeological sites in the Mediterranean. The second episode led the eventual city abandonment, and it is evidenced by good examples of column collapse, distortion, failure and breakdown of house and city walls, and pavement warping and disruptions documented during different archaeological excavations, which can be catalogued as secondary coseismic effects. Main damaged relicts observable today are the set of pop-up like arrays and warping developed in the ancient Roman pavement. Their analysis indicate an anomalous westwards ground displacement oblique to the main gentle southward slope of the topography, as also evidence failures, collapses and breakdown of walls and columns, suggesting that stress acted in a broad SW–NE/WSW–ENE orientation consistent whit the expectable motion along the largest NE–SW strike-slip faults of the zone, which in turn can be catalogued as seismic sources of moderate events (ca. 5 mb). Major disruptions and city abandonment were hesitantly related to relatively far strong earthquakes occurred during the late 4th century AD in the Mediterranean or western coast of Iberia by Menanteau et al. [Menanteau, L., Vanney, J.R., Zazo, C., 1983. Belo II : Belo et son environment (Detroit de Gibraltar), Etude physique d''un site antique. Pub. Casa de Velazquez, Serie Archeologie 4., Ed. Broccard, París.]. However, this study indicates that the occurrence of close moderate earthquakes jointly with the unstable character of the ground at the zone (site effect) is a more reliable hypothesis to explain the observed deformations. [Copyright &y& Elsevier]